Compaq EN Series Hardware Reference Manual page 18

2-10 Hardware Upgrades
10. Remove the subpanel 1 as described in the section "Removing
Bezel Blanks" and reposition it with the bezel blanks in the
proper orientation for the minitower configuration 2.
CAUTION: Hold the subpanel straight when you pull it away from the
front bezel. Pulling the subpanel away at an angle could damage the
pins that align it within the front bezel.
Changing from a Desktop 1 to a Minitower Configuration 2
11. Replace the subpanel, front bezel, and the computer access panel.
12. Reconnect the external equipment.